1. Field of the Invention
The invention relates to a transistor for active matrix display, a display unit comprising the said transistor and a method for producing the said transistor.
2. Description of Related Art
Since the advent of the portables and the need for flat display panels, electronic displays implementing thin-film transistor technology and liquid crystals have experienced a phenomenal growth, to the point where full-colour displays have been realised that can compete with cathode ray tube displays. Amorphous silicon thin-film transistors are extensively used as pixel charging devices in active matrix liquid crystal displays, principally because of its application to large glass substrates, low cost and remarkable matching with the requirements of liquid crystal driving. Over the last decade, a rapidly growing demand for high information content displays offering high performances (excellent contrast, homogeneity of colours, high luminance, large viewing angles . . . ) and having sizes down to “micro-panel”, for mobile phones for example, has nonetheless raised a huge interest for new technologies like organic light emissive diodes (OLED), polymer material based light emissive diodes (PLED), . . . The response time of OLED devices makes them perfectly suitable for video rate.
This demand adds constraints on the active material used in thin film transistors for active matrix displays, namely a higher stability and a more rapid charging than amorphous silicon (a-Si:H) thin films can provide. It is also necessary for a higher integration and to further reduce the cost of the display to process the driving circuits directly on the glass panel instead of connecting external circuits.
It is known that microcrystalline silicon (μc-Si:H) is compatible with amorphous silicon technology and can be directly deposited using plasma deposition technology at low temperatures without further thermal or laser treatment.
However, up to date studies of μc-Si:H thin films {ROCA I CABARROCAS, P et al.; J. Appl. Phys. 86 (1999) 7079 and references cited therein} have only reported linear mobilities similar to those of a-Si:H thin film transistors. Therefore, no improvement would be expected from these studies on the charging time of pixels using said μc-Si:H thin film transistors and on the driving circuit integration.